What creates the northern lights?
The Earth's magnetic field serves as a sort of shield for all the radiation and magnetic waves that crash over the planet. The particles in the solar wind are drawn toward the north and south poles by the magnetic field. As that happens, the particles mix with the molecules in our atmosphere -- oxygen, nitrogen, etc. -- and that interaction creates the colorful display.
The most commonly seen colors in the auroras are pink, green, yellow, blue, violet, orange, and white. Though, some of those colors are rarely seen. Space.com notes that when the particles combine with oxygen, you get yellow and green. When they interact with nitrogen, you'll see red, violent, and sometimes blue. Though, the site notes, it's more complicated than that because the type of collision and the altitude will impact the colors displayed as well. Red, for instance, only occurs at high altitudes. That color is rarely seen in northern regions where the aurora is most common because it will be taking place above the more easily visible colors appear at lower altitudes.
Where can you see the northern lights?
You'll want to get as far north as possible if you're traveling to see the aurora. Alaska and Canada are outstanding places to see the northern lights. Likewise, Norway, Sweden, Finland, Iceland, Greenland, and the northern coast of Russia are also known for providing a great hub. When solar activity is heightened, you will sometimes see the lights reach further south through Canada to states like Montana, North Dakota, Minnesota, Wisconsin, Michigan, and Maine. Occasionally, major solar events will bring the display even further south.
When do the northern lights happen?
The lights are present throughout the year, but winter is the best time. That's partly because there's less light pollution. Especially in northern countries where there's considerably more sunlight in the summer months. However, under the right conditions, you can see them any time of year. That's because solar winds are always crashing into Earth. But you'll only be able to see the auroral display when it's dark. If you're in the Arctic Circle during the summer, there's little to no darkness and, thus, no ability to see the northern lights. The best time tends to be between September and April.
If you're going to start hunting them down, there are a lot of tools you can use. About 40 hours after sunspot activity, you'll get a brighter and more active aurora that often reaches further south than usual. The Space Weather Prediction Center's 3-Day Aurora Forecast is a good place to keep tabs on how sunspot activity impacts aurora sightings. There are also tools like Aurorasaurus and the SWPC's 30-minute forecast that track the northern lights around the world and may help you find a good time to get a glimpse.